A relative of an 11-year-old autistic boy missing since the weekend in Riverside County was arrested Wednesday on suspicion of killing the boy.

The 16-year-old relative, who authorities refused to identify by name or relationship with the boy, was being held in the case of Terry Dewayne Smith, a highly functioning autistic child last seen Saturday night.

“This was a domestic issue within the residence,” Riverside County Sheriff’s Capt. John Hill said of the matter.

Shortly before 1 a.m. Wednesday, a slight body believed to be Terry’s was found in a shallow, dirt-covered grave, officials said. Investigators said the buried body was near a tree not far from the beige-and-brown home where Terry lived with his mother.

The last person who reportedly saw the 11-year-old was his 16-year-old stepbrother, who told police he told Terry to go home when he found his little brother following him as he walked to a local market. Terry’s stepbrother was reportedly tasked with taking care of him that night while his mother spent the evening out.

Terry’s mother returned about 1 a.m. Sunday and told police she thought she saw her son in bed when she checked on him before going to sleep, said sheriff’s Deputy Alberto Martinez. She reported him missing the next morning.

The sandy-blond-haired boy was said to have last been seen wearing blue basketball shorts and was described by his mother as a “high-functioning” autistic. Starting Sunday, search crews fanned across the Menifee area, aided by bloodhounds, helicopters and horseback riders.

Volunteers gathered in a prayer circle Wednesday as rumors spread that the hunt for Terry had taken a dramatic turn and that investigators were focusing on a search for remains.

“We will find a way to remember him in our hearts,” said Jenny Smith, who was one of the boy's fourth-grade teachers.

News that a body had been found was a crushing blow to the tight-knit community near Lake Elsinore and the approximately 1,000 searchers who had been looking for Terry since his disappearance was announced Sunday.

“He was a very good kid, very nice and sweet, never did anything wrong,” said a sorrowful Dallal Harb, the owner of the Menifee Market, a convenience store near the Smiths' property. Harb, 31, said Terry attended the same school as her two sons and that she would sometimes pick him up after school and bring him to her store for a snack before sending him home.

“I just don’t want to believe it,” she said. “I see what’s going on. But I just don’t want to believe it.”